Calibration of Photomultiplier Tube response for single photon detection using an LED light source

We calibrate the Photomultiplier (PMT) tube response to the single photon detection using an LED source. Precise determination of the PMT response to a single photon is crucial to calibrate PMT and benchmark with a simulation model to enhance the scintillation detector’s sensitivity and accuracy for the MOLLER experiment. The pulse width modulated signal (PWM) was used to operate the LED and produced a very low-intensity light pulse. Due to high sensitivity to subtle light levels, the test PMT was placed within a light-tight box to create an acceptable light yield to the PMT. A clear fiber connected the LED to the test PMT, facilitates the collection and transmission of the incident LED light. Three distinct types of attenuators, each with a natural density of 2.0, 1.3, and 1.0, were positioned between the LED and the clear fiber to adjust the LED intensity. The Pulse Width Modulated (PWM) signal functions as the trigger and once the PWM signal exceeds, the threshold trigger signal is activated. We measure the PMT response when the LED is ON. The characteristics of the PMT response are acquired using an analog-to-digital (ADC) unit and then data are analyzed by count histograms plotted using the ROOT data analysis software. The progress and results of PMT single photoelectron peak calibration will be provided.